A multitude of semiconductor devices are typically fabricated on a single semiconductor wafer substrate. Following a fabrication process sequence, individual devices or “die” are typically separated or “diced” from the substrate by sawing or laser scribing. These die are then incorporated within a packaging structure generally designed to seal the active area of the die and electrically interconnect device terminals with those of an external circuit. When devices are packaged using flip-chip bonding, solder beads or “bumps” often made of lead (Pb) or a lead alloy are reflowed and used to connect conductive terminals on the device to metal leads within the package. The active side of the device including the soldered interconnects is then encapsulated by an underfilling sealant that, when cured, provides an environmentally resistant barrier.
However, there is an ongoing effort by semiconductor device manufacturers to eliminate the use of many potentially hazardous materials including lead. Accordingly, other electrically conductive materials such as copper and copper alloys have been studied as potential replacements for lead-based solder interconnects. While copper interconnects have high electrical conductivity and improved mechanical strength compared with lead-based solders, copper is less ductile and thus is less able to absorb stress. As a result, shearing stresses between the packaging substrate and the surface of the die are often transferred by the relatively rigid copper interconnect to more brittle, back end of line (BEOL) and/or passivation layers within the die. Such stresses may be caused by, for example, a mismatch in the coefficient of thermal expansion (CTE) between the die and the packaging substrate, and can potentially fracture BEOL/passivation layers causing device failure. Therefore, an interconnecting structure capable of providing greater stress relief is desirable to prevent fracture of BEOL/passivation layers and improve the reliability of such devices.
Accordingly, it is desirable to provide semiconductor devices having a stress relief layer designed to absorb stress between a semiconductor die and a packaging substrate. Further, it is also desirable to provide methods for fabricating such semiconductor devices. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.